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32 Concerning Sense Perception Sense perception is a faculty of the soul that apprehends or distinguishes material things; the sense organs are the instruments, that is, the members through which we perceive; sensible things are those which fall under perception; and a sentient being is the living creature that has sense perception. There are five senses, and likewise five sense organs. The first sense is sight. The organs and instruments of sight are the nerves from the brain and the eyes. Sight perceives primarily color, but along with color it also distinguishes the colored body, its size and shape, the place where it is, the distance between, the number, motion and rest, the rough and the smooth, the even and the uneven, the sharp and the blunt, and the consistency, whether watery or earthy, that is, moist or dry. The second sense is hearing, which is the perception of voices and sounds. It distinguishes their high and low pitch, smoothness and roughness, and volume. Its organs are the soft nerves from the brain and the structure of the ears. Only man and the ape do not move their ears. The third sense is smell, which occurs through the nostrils sending vapors up to the brain, and it terminates at the ends of the anterior ventricles of the brain. It is perceptive and apprehensive of vapors. The most general distinction among vapors is fragrance and stench, and that which is in between, being neither fragrant nor foul-smelling. Fragrance comes from the liquids in bodies being perfectly concocted; a moderate condition from a moderate concoction; and stench from an imperfect or altogether non-concocted state. The fourth sense is taste. It is apprehensive or perceptive of flavors. Its organs are the tongue, and especially its tip, and the palate, which some call the roof of the mouth; in which are the flattened nerves carried from the brain, reporting to the governing faculty the perception, or sensation, that has occurred. The qualities of flavors, so-called, are these: sweetness, pungency, sourness, astringency, harshness, bitterness, saltiness, oiliness, stickiness; for taste is discerning of these. Water is without quality according to these qualities, for it has none of them. Astringency is an intensification and excess of harshness. The fifth sense is touch, which is common to all animals; it occurs from nerves sent from the brain to the whole body. For this reason the whole body, but also the other sense organs, have the sense of touch. Subject to touch are the cold and hot, the soft and hard, the viscous and brittle, the heavy and light; for these are known through touch alone. Common to both touch and sight are the rough and the smooth, the dry and the moist, the thick and the thin, up and down, place and size (when it is such that it can be encompassed in a single application of touch), the dense and the sparse (that is, rare), and the round (when it is small), and certain other shapes. Likewise it also perceives an approaching body, with memory and intellect, and also number up to two or three, and these small and easily encompassed. But sight perceives these things better than touch. It should be known that the Creator made each of the other sense organs double, so that if one were damaged, the other might fulfill the need; for two eyes and two ears and two nostrils and two tongues, but in some animals divided, as in snakes, and in others united, as in man; but touch is in the whole body, except for bones, nerves, nails, horns, hair, ligaments, and certain other such things. It should be known that sight sees in straight lines, but smell and hearing not only in a straight line, but from all directions. Touch and taste, however, perceive neither in a straight line nor from all directions, but only when they draw near to their proper objects of sense.

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32 Περὶ αἰσθήσεωσ Αἴσθησίς ἐστι δύναμις τῆς ψυχῆς ἀντιληπτικὴ τῶν ὑλῶν ἤγουν διαγνωστική· αἰσθητήρια δὲ τὰ ὄργανα ἤγουν τὰ μέλη, δι' ὧν αἰσθανόμεθα· αἰσθητὰ δὲ τὰ τῇ αἰσθήσει ὑποπίπτοντα· αἰσθητικὸν δὲ τὸ ζῷον τὸ ἔχον τὴν αἴσθησιν. Εἰσὶ δὲ αἰσθήσεις πέντε, ὁμοίως καὶ αἰσθητήρια πέντε. Πρώτη αἴσθησις ὅρασις. Αἰσθητήρια δὲ καὶ ὄργανα τῆς ὁράσεως τὰ ἐξ ἐγκεφάλου νεῦρα καὶ οἱ ὀφθαλμοί. Αἰσθάνεται δὲ ἡ ὄψις κατὰ πρῶτον μὲν λόγον τοῦ χρώματος, συνδιαγινώσκει δὲ τῷ χρώματι καὶ τὸ κεχρωσμένον σῶμα καὶ τὸ μέγεθος αὐτοῦ καὶ τὸ σχῆμα καὶ τὸν τόπον, ἔνθα ἐστί, καὶ τὸ διάστημα τὸ μεταξὺ καὶ τὸν ἀριθμὸν κίνησίν τε καὶ στάσιν καὶ τὸ τραχὺ καὶ λεῖον καὶ ὁμαλὸν καὶ ἀνώμαλον καὶ τὸ ὀξὺ καὶ τὸ ἀμβλὺ καὶ τὴν σύστασιν, εἴτε ὑδατώδης, εἴτε γεώδης ἤγουν ὑγρὰ ἢ ξηρά. ∆ευτέρα αἴσθησίς ἐστιν ἀκοὴ τῶν φωνῶν καὶ τῶν ψόφων οὖσα αἰσθητική. ∆ιαγινώσκει δὲ αὐτῶν τὴν ὀξύτητα καὶ τὴν βαρύτητα λειότητά τε καὶ τραχύτητα καὶ μέγεθος. Ὄργανα δὲ αὐτῆς τὰ νεῦρα τὰ ἐξ ἐγκεφάλου τὰ μαλακὰ καὶ τῶν ὤτων ἡ κατασκευή. Μόνος δὲ ἄνθρωπος καὶ πίθηκος οὐ κινοῦσι τὰ ὦτα. Τρίτη αἴσθησις ὄσφρησις, ἥτις γίνεται μὲν διὰ τῶν ῥινῶν ἀναπεμπουσῶν τοὺς ἀτμοὺς ἐπὶ τὸν ἐγκέφαλον, περαίνεται δὲ εἰς τὰ πέρατα τῶν προσθίων κοιλιῶν τοῦ ἐγκεφάλου. Ἔστι δὲ αἰσθητικὴ καὶ ἀντιληπτικὴ τῶν ἀτμῶν. Τῶν δὲ ἀτμῶν ἡ γενικωτάτη διαφορά ἐστιν εὐωδία καὶ δυσωδία καὶ τὸ μέσον τούτων, ὃ μήτε εὐῶδές ἐστι μήτε δυσῶδες. Γίνεται δὲ εὐωδία τῶν ὑγρῶν τῶν ἐν τοῖς σώμασιν ἀκριβῶς πεφθέντων, μέσως δὲ μέση διάθεσις· καταδεέστερον δὲ ἢ μηδὲ ὅλως πεφθέντων ἡ δυσωδία γίνεται. Τετάρτη αἴσθησις ἡ γεῦσις. Ἔστι δὲ τῶν χυμῶν ἀντιληπτικὴ ἤγουν αἰσθητική. Ὄργανα δὲ αὐτῆς ἡ γλῶσσα καὶ ταύτης πλέον τὸ ἄκρον καὶ ἡ ὑπερῴα, ἣν καλοῦσί τινες οὐρανίσκον· ἐν οἷς ἐστι τὰ ἐξ ἐγκεφάλου φερόμενα νεῦρα πεπλατυσμένα καὶ ἀπαγγέλλοντα τῷ ἡγεμονικῷ τὴν γενομένην ἀντίληψιν ἤγουν αἴσθησιν. Αἱ δὲ καλούμεναι γευστικαὶ ποιότητες τῶν χυμῶν εἰσιν αὗται· γλυκύτης, δριμύτης, ὀξύτης, στρυφνότης, αὐστηρότης, πικρότης, ἁλμυρότης, λιπαρότης, γλισχρότης· τούτων γάρ ἐστιν ἡ γεῦσις διαγνωστική. Τὸ δὲ ὕδωρ ἄποιόν ἐστι κατὰ ταύτας τὰς ποιότητας· οὐδεμίαν γὰρ αὐτῶν ἔχει. Ἡ δὲ στρυφνότης ἐπίτασις καὶ πλεονασμός ἐστι τῆς αὐστηρότητος. Πέμπτη αἴσθησίς ἐστιν ἡ ἁφή, ἥτις κοινή ἐστι πάντων τῶν ζῴων· ἥτις γίνεται ἐκ τοῦ ἐγκεφάλου πεμπομένων νεύρων εἰς ὅλον τὸ σῶμα. ∆ιὸ καὶ ὅλον τὸ σῶμα, ἀλλὰ καὶ τὰ ἄλλα αἰσθητήρια τὴν τῆς ἁφῆς ἔχουσιν αἴσθησιν. Ὑπόκειται δὲ τῇ ἁφῇ τὸ ψυχρὸν καὶ θερμόν, τό τε μαλακὸν καὶ σκληρὸν καὶ γλίσχρον καὶ κραῦρον, βαρύ τε καὶ κοῦφον· διὰ μόνης γὰρ ἁφῆς ταῦτα γνωρίζεται. Κοινὰ δὲ ἁφῆς καὶ ὄψεως τό τε τραχὺ καὶ λεῖον, τό τε ξηρὸν καὶ ὑγρόν, παχύ τε καὶ λεπτόν, ἄνω τε καὶ κάτω καὶ ὁ τόπος καὶ τὸ μέγεθος, ὅταν εἴη τοιοῦτο ὡς κατὰ μίαν προσβολὴν τῆς ἁφῆς περιλαμβάνεσθαι, καὶ τὸ πυκνόν τε καὶ μανὸν ἤγουν ἀραιὸν καὶ τὸ στρογγύλον, ὅταν εἴη μικρόν, καὶ ἄλλα τινὰ σχήματα. Ὁμοίως δὲ καὶ τοῦ πλησιάζοντος σώματος αἰσθάνεται, σὺν τῇ μνήμῃ δὲ καὶ τῇ διανοίᾳ, ὡσαύτως δὲ καὶ ἀριθμοῦ μέχρι δύο ἢ τριῶν καὶ τούτων μικρῶν καὶ ῥᾳδίως περιλαμβανομένων. Τούτων δὲ μᾶλλον τῆς ἁφῆς ἡ ὅρασις ἀντιλαμβάνεται. Χρὴ γινώσκειν, ὡς ἕκαστον τῶν ἄλλων αἰσθητηρίων διπλοῦν ὁ δημιουργὸς κατεσκεύασεν, ἵνα τοῦ ἑνὸς βλαπτομένου τὸ ἕτερον ἀναπληροῖ τὴν χρείαν· δύο γὰρ ὀφθαλμοὺς καὶ δύο ὦτα καὶ δύο πόρους τῆς ῥινὸς καὶ δύο γλώσσας, ἀλλ' ἐν τοῖς μὲν τῶν ζῴων διῃρημένας ὡς ἐν τοῖς ὄφεσιν, ἐν τοῖς δὲ ἡνωμένας ὡς ἐν τῷ ἀνθρώπῳ· τὴν δὲ ἁφὴν ἐν ὅλῳ τῷ σώματι πλὴν ὀστέων καὶ νεύρων ὀνύχων τε καὶ κεράτων καὶ τριχῶν καὶ συνδέσμων καὶ ἄλλων τινῶν τοιούτων. Χρὴ γινώσκειν, ὅτι ἡ μὲν ὄψις κατ' εὐθείας γραμμὰς ὁρᾷ, ἡ δὲ ὄσφρησις καὶ ἡ ἀκοὴ οὐ κατ' εὐθεῖαν μόνον, ἀλλὰ πανταχόθεν. Ἡ δὲ ἁφὴ καὶ ἡ γεῦσις οὐδὲ κατ' εὐθεῖαν οὐδὲ πανταχόθεν γνωρίζουσιν, ἀλλὰ τότε μόνον, ὅταν αὐτοῖς πλησιάσωσι τοῖς ἰδίοις αἰσθητοῖς.